Glow discharge means for temperature control



April 23, 1935. c. A; SABBAH 1,998,943 v GLOW DISCHARGE MEANS FOR TEMPERATURE CONTROL Filed Oct. 31, 1930 7'0 HEAT/N6 CURRENT SOUfiGf Invehbor: Camil' A Sabbah,

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Patented Apr. 23, 1935 UNITED STATES PATENT OFFICE;

GLOW DISCHARGE MEANS FOR TEMPERA- TURE CONTROL Camll A. Sabbah, Schenectady, N. Y., assignor to H General Electric Company, a corporation of New York Application October 31, 1930, Serial No. 492,586

17 Claims. (01. 219' 2o) My invention relates to the indication and conrent through condenser I2 is approximately 3 trol of temperature, for example the temperaamperes at a frequency of 100 cycles per second. ture of a medium within afurnace, and has for To vary the pressure of the mercury vapor in its principal object the provision of an improved tube and thereby to control the oscillatory 5 temperature indicating and controlling system current in circuit 9, a mercury pool ll, sealed 5 comprising a glow discharge device. in a vessel I4 preferably of metal and connected Various temperature responsive devices have to the glow discharge tube 5 by a tube l5 also been proposed in the past to indicate or control preferably of metal, is arranged to absorb heat the temperature of a fluid medium, such, for exfrom a medium in which temperature changes ample as the heated air or gas within an electric are to be indicated and the temperature of which 10 furnace. In accordance with my invention, is to be controlled. In the present embodiment changes in the temperature of the medium withof the invention heat is supplied to mercury pool in such furnaces may be visually indicated and I3 from a medium in a container l6 which-may the temperature of the medium may be mainbe an electric furnace having heating means tained within small limits, by a simple and efcomprising a resistor or heater i1 supplied with 15 fective temperature" responsive system in which current from a suitable source or may be a chama glow discharge tube is utilized to produce curber derived from an electric furnace with much rents in accordance with the temperature to be lower temperature but always proportional to the indicated and controlled; In this system an intemperature of the furnace.

termittent discharge in a glow discharge tube, It will be understood that when the pressure of 20 varying in accordance with changes in the temthe mercury vapor in glow discharge tube 5 is perature of the heated medium, provides an inbelow a given value oscillations occur in circuit 9 dication of a drop in temperature within the and a glow discharge appears between the eleci'urnace; and further, forms a switching means trodes l, 8 in the tube, these oscillations being to control the flow of heating current to the due to intermittent discharges of the condenser B- I! through the tube 5. When, however, the pres- My invention will be better understood from sure of the mercury vapor in tube 5 becomes the following description when considered in greater than that maximum pressure'at which a connection with the accompanying drawing and glow discharge will take-place between electrodes its scope will be pointed out in the appended I, 8,it will be noted that after the glow discharge 30 claimsis extinguished, as the condenser voltage drops Referring to the drawing, Fig. 1 is a diagrambelow the maintaining potential, the tube cannot matic view of a temperature responsive system glow again, even though the condenser potential in accordance with my invention, and Fig. 2 reaches the full potential of source I I, until the 3 is a diagrammatic view of a temperature repressure of the mercury vapor has gone down to sponsive system in accordance with the inventhe above stated maximum value. It will be tion, in which temperature control of a medium noted further that the mercury vapor pressure in is effected automatically. tube 5 is increased when mercury in pool I3 is In the embodiment of the invention illustrated vaporized by heat transferred thereto from the 40 in Fig. l, the temperature responsive system comsurrounding medium in container 5.. There- 40 prises a glow discharge device 5 which is profore, in operation of the system shown in Fig. l, vided for the purpose of producing intermittent the oscillations in circuit 9 and the accompanying glow discharges. This glow discharge device or glow discharge in tube 5 when once started will tube which may in certain applications, continue until a rise in temperature of the mediof relatively small dimensions, for example even um surrounding mercury pool i3 causes a rise 45 0f the dime sions of a flashli ht bul p f r ly of pressure in tube 5, due to vaporizing of mercury contains neon at a pressure of 7 mm. of mercury, in pool l3, to a value above that at which the glow helium at a pressure of 14 mm. of mercury, and discharge may take place. When this value is mercury vapor supplied from a mercury pool reached the glow in tube B'suddenly disappears, 6 within the tube. In order to produce an oscilindicating that the temperature of the medium latory current in the tube 5, the electrodes 1, 8 in container I 6 has risen above the predetermined are connected in a circuit 9 comprising a 500 value. If the heat supply through heater eleohm resistor 10 and 250 volt current source ll ment I 1 is then reduced or cut oil, the oscillations in series with the electrodes, and a 1'7 mf. conin circuit?! and the discharge in glow discharge denser I! in shunt therewith. The resulting curtube 5 will recommence after a short period,

varyin for example, from three to litteen seconds. The current source which supplies the heating element, resistor l1, may be normally controlled in accordance with the visual indications provided directly by the light 0! the discharge in glow discharge tube 5 or in accordance with the indications of suitable meters. It will be readily understood that any suitable means operated in accordance with the discharge current in circuit 5 may be utilized to control the heating current which is supplied from the source connected to heating member I1.

An oscillatory discharge in tube 5 is desirable since, during each oscillation, the potential impressed on the tube by condenser l2 drops below the are maintaining potential, and, therefore, under conditions of rising pressure in the tube the glow is cut oil. positively at the first oscillation of condenser potential which occurs after the tube pressure has risen to approximately its predetermined maximum value at which a glow discharge in tube 5 may start.

It has been found that by the use of the glow discharge device 5 and its associated circuits in the manner described herein the temperature within the container l6 may be maintained practically constant, varying from a predetermined value by only a small fraction of a degree. It will be understood that the kind and quantity or gas or vapor in glow discharge tube 5 and the length of the tube l5 interconnecting glow discharge tube 5 and the mercury pool H are such that the discharge in tube 5 disappears when the temperature of the medium surrounding pool it reaches a predetermined maximum value. If the tube I5 is lengthened, thereby adding an appreciable body of gas to that contained in discharge tube 5, the temperature to which the medium surrounding pool I3 must rise in order to produce pressure in tube 5 sumcient to stop the discharge therein is correspondingly higher. If the tube I5 is made relatively short, thereby decreasing the total body of gas in the discharge tube system, the temperature required, in the medium about pool 13, to produce sufllcient pressure to stop the discharge is correspondingly lowered. In certain cases the tube length required may be very short, or even may be zero, in which latter case the glow discharge tube 5 itself, containing the mercury pool 6, may function as the vessel H having the mercury pool l3 therein and the mercury pool l3 and its container and connecting tube may be omitted.

.The embodiment of the invention illustrated in Fig. 2, is similar in general to that illustrated in Fig. 1 but in the arrangement of Fig. 2 the heating means for the medium enclosed by the container l5 includes the resistor l5 forming part of the oscillation circuit 9 described in connection with the system of Fig. 1.

In the operation of the system of Fig. 2, assuming that suflicient heat may be supplied by resistor I0, during periods of oscillation of circuit 5 and of passage of the discharge in glow discharge tube 5, to raise the temperature of the medium in container l5 above a predetermined value, it will be seen that when once started the oscillations in circuit 5, and the accompanying flow of current through the glow discharge tube 5 and the heating elementor resistor ll within container l5, will continue until a rise of temperature in the medium about the mercury pool l3 causes a rise or pressure in tube 5 to a value above that atwhich the discharge in this tube can occur. When this limiting pressure is reached the 810W in tube 5 ceases and with it the heating current 1 in resistor III. In a few seconds the temperature of the medium surrounding mercury pool ll drops a fraction of a degree. The vapor pressure in tube 5 drops correspondingly, this vapor pressure drop being suflicient to permit again the initiation of oscillations in circuit 5 and the accompanying flow of current in glow discharge tube 5 and heating member or resistor II. The cycles of operation and non-operation above described continue alternately and the temperature of the medium in container Iiis thereiore maintained, within close limits, at a predetermined value.

The glow discharge tube 5 has been described herein as containing neon and helium in certain proportions and mercury vapor varying in pressure in accordance with heat conditions. It is to be understood, however, that the gas or vapor contents of the discharge device 5 may be varied in quality and quantity for purposes 0! adjustment to meet varying conditions, it being only necessary, tor the purpose of carrying the invention into effect, that means including a vaporizable material, liquid or solid, be arranged to provide the proper vapor pressure in the device I to extinguish the glow discharge therein under predetermined temperature conditions.

In case of high current outputs the glow tube may have at least one mercury electrode to bring the cathode drop down to about 20 volts to provent excessive heating of the tube. If desired the apparatus may also be so arranged that mercury condensed in the tubes may be automatically returned to the containers II to maintain a body of mercury therein at all times.

whatlclaimasnewanddesiretosecureby Letters Patent 0! the United States, is:

'l. The combination of a glow discharge device. means to maintain a discharge in said device after initiation of said discharge due to drop of the gas pressure in said device, said means being operable only at such time as the pressure of the gas within the device has a value substantially equal to a predetermined value and values below said predetermined value, a heat source external to said discharge device, and means dependent upon heat from said source to vary said gas pressure sufllciently to interrupt said discharge in said device at said value substantially equal to a predetermined value, the initiation and the stopping of said discharge being in response only to said varying pressure due to heat from said source.

2. The combination of a glow discharge device containing a vapor, a heat source external to said discharge device, means to maintain a discharge in said device after initiation of said discharge due to drop of the vapor pressure in said device, said means being operable only at such time as the pressure of said vapor within the device has a value substantially equal to a predetermined value and values below said predetermined value, and means responsive to heat from said source to increase the pressure of said vapor from a value at which discharge occurs in said device to a value at which said discharge is prevented, the initiation and the stopping of said discharge being in response only to thevariatlon of said pressure due to heat from said source.

3. The combination oi a container, a medium therein varying in temperature, a glow discharge device, means to maintain a periodic discharge in said device after initiation of said discharge due to drop of the gas pressure in said device, said means being operable only at such time as the pressure of the gas within the device has a value substantially equal to a predetermined value and values below said predetermined value, and means dependent on the temperature of said medium to vary said gas pressure over a range including saidpredetermined value whereby an indication of said temperature i." produced, the initiation and the stopping 0! said discharge being in response only to said varying gas pressure due to variation of temperature oi said medium.

4. In a system responsive to the temperature of a medium. a glow discharge device, means to maintain a discharge'in said device after initiation 0! said discharge due to drop of the gas pressure in said device, said means being operable only at such time as the pressure of the gas within said device has a value substantially equal to a predetermined value and values below said predetermined value, and means comprising a vaporizable material heated by said medium for varying said gas pressure in said device over a range including said predetermined value whereby an indication oi! said temperature is produced, the initiation and the stopping of said. discharge be ing in response only to said varying pressure due to heat from said medium.

5. In a system comprising a medium whose temperature is to be controlled, a glow discharge device having a vapor therein, means external to said discharge device to heat said medium, means.

to maintain a periodic discharge in said device after initiation of said discharge due to drop of the gas pressure in said device,'said last-named means being operable only at such time as the pressure 01 the gas within the device has a value substantially equal to a predetermined value and values below said predetermined value, and means dependent upon the temperature oi' said medium to vary said gas pressure suiiiciently to interrupt said discharge in said device, the initiation and the stopping of said discharge being in response only to said varying pressure due toheat from said medium.

6. In a temperature control system, a medium, a resistor and a current source connected thereto for heating said medium, a glow discharge device having a vapor therein, means including said resister and said current source for causing discharges in said glow discharge device, and means comprising material vaporizable by heat from said medium to increase 'the vapor pressure in said device suiiiciently to prevent the occurrence of discharges in said device.

7. In a system for controlling the temperature of a medium, a glow discharge device, a circuit including a resistor and a current source and a condenser for causing the flow of periodic discharge currents in said device, said resistor being in contact with said medium to supply heat thereto due to said discharge currents, said glow discharge device containing a vapor, and material vaporizable to produce additional quantities of said vapor in said device and arranged to be vaporized by heat from said medium to increase the vapor pressure in said device sufficiently to prevent the flow of said periodic discharge currents therein.

8. In a system responsive to the temperature of a medium, a glow discharge device containing mercury vapor, a heater element in contact with said medium, a circuit for causing periodic discharges in said device including said heater element and a current source and a condenser, and a body of mercury arranged to be vaporized by heat irom said medium to increase the pressure oithe mercury vapor in said device.

' 9. In a system responsive to the temperature of a medium, a glow discharge device, a circuit for causing periodic discharges in said device. including in series therewith a resistor and a current supply source and including a condenser in shunt to said device, means to heat said medium, said glow discharge device containing a vapor. and material vaporizable to produce additional quantities of said vapor in'said device and arranged to be vaporized by heat from said medium.

10. In a system responsive to the temperature of a medium, a glow discharge device, a circuit ior causing periodic discharges in said device including in series therewith a resistor and a current supply source and including a condenser in shunt to said device, means to heat said medium, said device containing mercury vapor, and a body o't mercury arranged to be vaporized by heat from said medium to increase thepressure 0! the mercury vapor in said device.

11. The combination of a glow discharge device, a heat source external to said glow dischargedevice, means to maintain a discharge in said device after-initiation oi said discharge due to drop of the gas pressure in said device, said means being operable only 'at such time as the pressure of the gas within said device has a value substantially equal to a predetermined value and values below said predetermined value, and means responsive to the heat from said source to increase the pressure or said gas from a value at which discharge occurs in said device to a value at which said discharge is prevented, the initiation and the stopping of said discharge being in response only to the varying pressure of said gas due to heat from said source.

12. The combination of a glow-discharge device containing a vapor, a heat source external to said device, means to maintain a discharge in said device after initiation of said discharge due to drop in the vapor pressure in said device, said means being operable only at such time as the pressure of the vapor in said device has a value substantially equal to a predetermined value and values below said predetermined value, and means responsive to the heat from said source to increase the pressure of said vapor from a value at which discharge occurs in said device to a value at which said discharge is prevented, the initia tion and the stopping of said discharge being in response only to varying pressure of said vapor due to heat from said source.

13. The combination, in a temperature responsive system, oi a space the temperature within which is to be maintained at predetermined values, a vessel containing an attenuated gas having at least a portion arranged within said space, heating means within said space, means to maintain a discharge within said vessel after initiation of said discharge due to drop in the gas pressure in -:said vessel, said last named means being operable only at such time as the pressure 01' said gas has a value substantially equal to a predetermined value and values below said predetermined value, and means dependent upon the heat in said space to vary said gas pressure suiliciently to initiate discharge in said vessel, the initiation and the stopping of said discharge being in response only to said varying pressure due to the heat in said space.

14. The combination, in a temperature responsive system, of a space the temperature within which is to be maintained within a predeter- 1g mined range, a vessel containing attenuated gas having at least a portion arrangedwithin said space, heating means within said space,-a pair of electrodes arranged within said gas, means to maintain a discharge between said electrodes after initiation oi! said discharge due to drop in the gas pressure in said vessel, said last-named means being operable'only at such time as the pressure of said gas has a value substantialLy equal to a predetermined value and values below said predetermined value, and means dependent upontheheatinsaidspacetovarysaidgas pressure sumciently to initiate discharge in said vessel, the initiation and the stopp of said discharge being in response only to said varying pressure due to the heat in said space,

15. The combination, in a temperature responsive system, of a space the temperature within which is to be controlled, a glow-discharge device containing an attenuated gas having at least a portion arranged within said space, heating means in said space, and means responsive to pressure oi the gas to initiate a succession oi discharges in said glow-discharge device to control said heating means.

16. A temperature indicating system comprising a glow discharge device having a plurality oi electrodes spaced apart in an attenuated gas and adjusted to break down and pass current only at such time as the pressure of said gas has a value substantially equal to a predetermined value, and means to yary the pressure or said gas in accordance with the temperature to be indicated and over a range sumcient to cause said device to break down whereby an indication of said temperature is produced.

17. A temperature indicating system comprising a glow discharge device having a plurality of electrodes, spaced apart in an attenuated gas and adjusted to break down and pass current only at such time as the pressure of said gas has a value substantially equal to a predetermined value, and means to vary the pressure oi said gas in accordance with the temperature to be indicated and over a range sufficient to cause said device to break down whereby an indication of said temperature is produced, the initiation and the stopping of the flow of said current being in response only to the variation 01 said gaspres sure due to variation of said temperature.

a cam. A. SABBAH.

DISCLAIMER 1,Q98,943.--Oamil A; Sabbah, Schenectady, N. Y. Gnow DISCHARGE MEANS FOR TEMPERATURE CONTROL. Patent dated Ayril 23, 1935. Disclaimer filed March 22, 1938, by the assignee, General E ectr'ic Company. Hereby disclaims claims 1, 2, 3, 4, 5, 9, 10, 11, 12, 13, 14, 15, 16, and 17 of said Letters Patent.

[Oflic'ial Gazette, April 19, 1938.]

DISCLAIMER 1,998,943.-C'amil A; Sabbah, Schenectady, N. Y. GLOW DISCHARGE MEANs F R TEMPERATURE CONTROL. Patent dated April 23,1935. Disclaimer filed March 22, 1938, by the assignee, General Electric Company; Hereby disclaims claims 1, 2, 3, 4, 5, 9, 10, 11, 12, 13, 14, 15, 16, and 17 of said Letters Patent.

[Qfl'ic'ial Gazette, April 19, 1938.] 

